An electronic device often has a non-volatile memory such as ROM where firmware, that is, programs, control data, etc. has been recorded. The programs stored in this non-volatile memory are executed to perform various functions. Recently, a rewritable non-volatile memory such as a flash memory has been used as such firmware. In many electronic devices that have been already provided, such firmware can be rewritten after factory shipment so that another function can be added to the firmware or the version of the firmware can be upgraded. Patent Document 1 is one of technical documents about rewriting of such firmware. This Patent Document 1 discloses an audio signal processing apparatus having a reproduction mode and an upgrade mode. In the reproduction mode, digital data read from a CD are reproduced as music. On the other hand, in the upgrade mode, firmware is rewritten by digital data read from an upgrade CD so that functions can be upgraded.
Patent Document 1: JP-A-2002-149428